The present invention relates generally to a pulse tube refrigerator (PTR), and particularly to a pulse tube refrigeration system (PTRS) with an auxiliary power source.
The introduction of the magnetic resonance imaging (MRI) scanner in the 1970s has revolutionized diagnostic medicine. The MRI scanner employs a magnetic field and a plurality of radio frequency signals to permit instant mapping and analysis of bodily tissue.
A typical MRI scanner includes superconducting magnets. As one skilled in the art would understand, a superconducting magnet is comprised of coils or windings of wire through which a current of electricity is passed for generating the magnetic field. Further, the wire is typically cooled by helium liquid so as to render the wire superconducting, a current therethrough persistent, and the magnet independent of the power system.
Current MRI scanners may use a pulse tube refrigerator (PTR) to cool the superconducting magnet. The PTR typically includes an electric compressor and a rotary valve driven by an electric motor. Unless an uninterruptible power supply provides an MRI scanner with the necessary power, an MRI scanner usually must shut down during a power failure. Moreover, a superconducting magnet may quench if it has an insufficient liquid cryogen reserve. As one skilled in the art would understand, quenching describes the process in which the superconductor becomes resistive thereby expelling nearly all of the cryogens, blowing the burst disk, and ultimately necessitating magnet re-ramp. As a result, costly processes may be required to return the magnet to operating condition. For example, the expensive endeavor of reshimming the magnetic field on re-ramp may be required. Such a result is clearly undesirable.
Therefore, a need exists to provide a pulse tube refrigeration system (PTRS) that continues to operate the PTR of an MRI scanner in the event of a power failure, i.e. ride-through a power outage.
It is an object of the present invention to permit a pulse tube refrigerator (PTR) to operate in the event of an electrical power supply failure. It is yet another object of the present invention to improve the cooling efficiency of the PTR.
In accordance with the above and other objects of the present invention, a method and system are provided for maintaining proper fluid pressure within a PTR during an electrical power supply failure.
There is disclosed herein a method and system for providing a ridethrough reserve for a PTR. The method and system include a pressurized tank containing a fluid used to provide a desired fluid pressure and an auxiliary power to a PTR during an electrical power supply failure. A pressure regulation valve (pressure valve) releases the fluid from the pressurized tank into the PTR. A power regulation valve (power valve) releases from the pressurized tank a driving gas volume for driving a pneumatic motor. The pneumatic motor drives a rotary valve of the PTR. A release valve releases fluid from the PTR so as to lower the fluid pressure to a predetermined pressure range.
Other objects and advantages of the present invention will become apparent upon reading the following detailed description and appended claims, and upon reference to the accompanying drawings.